The subject matter of the present invention relates to a release mechanism associated with a perforating apparatus adapted to be disposed in a wellbore, and more particularly, to an automatic tubing release mechanism connected between a perforating apparatus and a tubing for shattering a frangible breakup tube thereby automatically releasing the perforating apparatus from the tubing in response to a detonation was passing. Throw in the break-up tube.
It is sometimes desirable when perforating a wellbore to automatically disconnect a perforating gun from a tubing in response to a detonation of the perforating gun and drop the perforating gun to a bottom of the wellbore. This is especially true in permanent completions where no additional wireline or tubing runs are desired. It is also desirable to automatically disconnect the perforating gun from the tubing following detonation when perforating in certain specific formations where, following detonation, an inflow of formation fluids will cause the perforating gun string to sand up and become stuck in the casing. Many automatic releases are presently available from various manufacturers. Such releases usually use the detonation of the firing head or detonating cord to trigger the release. Many utilize the hydrostatic fluids, entering through the open holes of a spent or expired perforating gun, to shift a piston or a sleeve and to unlock and separate the perforating gun from the end of a tubing. For example, U.S. Pat. No. 4,526,233 to Stout discloses a releasable coupling for tubing conveyed perforating guns wherein a pressurized fluid resultant from detonation of the perforating gun shifts an annular piston thereby unlatching a radially shiftable latch means from one position to another position and allowing the perforating gun to separate from the tubing. In addition, U.S. Pat. No. 4,815,540 to Wallbillich discloses a method and apparatus for releasing a well perforating gun from a supporting tubing wherein a fluid pressure in an annular fluid pressure chamber supplied from the tubing string shearably releases a piston causing the piston to move out of engagement with collet locking heads thereby allowing the collet heads to shift radially to clear a downwardly facing annular surface and releasing the perforating gun form the tubing, the gun falling to a bottom of the wellbore.
One problem with many of these prior releases results form a pressure leak in the gun; if a gun leaks pressure form the wellbore to the inside of the gun string, this pressure may prematurely activate the release and separate the guns from the end of the tubing Another problem with these prior releases involves clogged or plugged shaped charge holes; when heavy muds exist in the wellbore, the shot shaped charge holes in the perforating gun can become plugged with charge debris and mud, thereby preventing adequate fluid pressure form shifting the release piston.